Plz enlighten in the calculation of GAY LUSSAC'S Law of Chemical combination by Volume.I get lost @ "EXPECTED VOLUME AFTER SPARKING". Example: 50cm3 of hydrogen are sparked with 20cm3 of oxygen at 100 deg celsius and 1 atmosphere.What is d total volume of the residual gases?(JAMB).

Now d eqn of the reactn is 2H2 + O2--> 2H2O. TO CALCULATE VOL OF RESIDUAL GAS, SINCE 1MOLE OF O2 IS 20CM3, 2MOLES OF H2 WILL BE 20 * 2 =40cm3. Meanwhile vol of hydrogen gas givn is 50cm3 and 40cm3 was used for the sparking(reaction). Vol of unreacted gas is 50 - 40 = 10CM3. VOL OF RESIDUAL GAS IS =vol of unreacted gas + vol of product gas.ie 10cm3 + 40cm3 = 50cm3.